We study $N=1$ supersymmetric $SO(10)$ gauge theory with a field in the spinorial representaition and $N_f$ ($\leq8$) fields in the defining representation. It is shown that this theory for $N_f=7,8$ has a dual description, which is $N=1$ supersymmetric $SU(N_f-5)$ gauge theory. Its matter content for $N_f=7$ is different { }from the one for $N_f=8$; for $N_f=7$, it contains $8$ fields in the anti-fundamental representation. For $N_f=8$, a rank-$2$ symmetric tensor and one field in the fundamental representation appears in addition to them. This duality connects along the flat direction to the duality between chiral and vector gauge theory found by Pouliot.
Categories: hep-th hep-ph